The present invention relates to a hydraulic brake system, and more particularly to a hydraulic brake system with a skid control function.
Japanese Patent Application First (unexamined) Publication No. 60-33158 discloses a hydraulic brake system with a skid control function. The known hydraulic brake system has an electromagnetic inflow valve fluidly disposed between a master cylinder and a wheel cylinder, a fixed orifice fluidly disposed between the inflow valve and the master cylinder and an electromagnetic normally open orifice bypass valve arranged in parallel to this fixed orifice. In skid control, the electromagnetic normally open orifice bypass valve is closed, and flow of hydraulic fluid forced out of the master cylinder toward the wheel cylinder is restricted by the fixed orifice. During usual braking, the electromagnetic normally open orifice bypass valve is opened and flow of hydraulic fluid forced out of the master cylinder into the wheel cylinder is unrestricted. Owing to the provision of this fixed orifice, occurrence of pressure urge during skid control is prevented.
An object of the present invention is to improve a hydraulic brake system of the above kind such that, without an electromagnetic orifice bypass valve, restriction of flow of hydraulic fluid forced to of a master cylinder toward a wheel cylinder is controlled.